Objectives: 1.) The determination of the effects of variation in components of semi-synthetic diets on lipid metabolism in baboons and vervet monkeys. The diet (14% coconut oil, 40% carbohydrate, 25% protein, 15% fiber) will vary only in the last two components. Proteins to be tested: casein, soya, wheat gluten. Fibers under consideration: Glucose, alfalfa, wheat straw. To be determined: cholesterol absorption, pool size and production rate; bile acid spectrum and pool size; atherogenesis; serum and liver lipids. 2.) Comparison of lactose and lactose-cholesterol diets in vervet monkeys and baboons. 3.) Investigate effects of semi-purified diets in aged Rhesus monkeys in Johannesburg, if colony can be made available.